Subject: Re: [CR] Campy NR Headset & Brinelling
>
> On Nov 23, 2009, at 12:59 PM, <RDF1249@aol.com> wrote:
>
>> I don't think impact is the cause of brinelling.
>
> Correct. It's caused by fretting.
> Phil Brown
> Tired already in Oakland, Calif.
Fretting is the bonding between mating parts that pulls metal away from surfaces. That is mostly the inevitable result of lubrication failure and/or absence of lubrication.
The case of the quickly-damaged headset is merely dents from over-loading, and it's not just certain NR headsets. I've never been able to damage a headset by deliberate, severe overtightening, it has to be ridden tight to dent the races. I once brinnelled a new 7402 Dura-Ace headset on the first ride, and it was mildly overtightened at most, imperceptible with levers/cables on board. Sadly, I loaded the bearings sans retainers on the first go, meaning I couldn't then just do the retainer-removal trick to cure it. The retainer, if re-installed, doesn't have the same ability to space the balls solidly as does a full race of ~24 balls, so a cure was elusive and I replaced the headset with an off-topic cartridge unit. I've noticed that those (off-topic cartridge headsets) seem to have much greater resistance to overtightening damage, as I've routinely set up MTB's with noticeable drag using the off-topic top cap to tension the bearings with no harm done. I should note that a quill stem was not used in these cases.
David Snyder
Auburn, CA usa